Have you ever seen a really good distance runner that had a bodybuilders build? I didn't think so. The body adapts to the stressor presented. Tell your body through running hard every day and it will adapt to improving that. Tell your body through lifting hard and it will adapt to improving that.

If you are truly running hard it will limit strength gains. The body is using it's survival adaptation energy toward building a better runner. It all depends on what your goals are. If you want to bodybuild you can do a limited amount of running and it will be a compromise. If you want to be a good runner with a good build that's another compromise in the weight room. Most bodybuilders do really easy cardio like walking on a treadmill or going easy on one of the cardio machines. If any bodybuilder started to run a hard 5 miles every day his lifting would suffer. Same goes for a runner who decides to lift to much.

Cardio is great for bodybuilding. Training hard core cardio like running 5 miles a day will kill your lifting. Run a hard 5 miles and train legs the day after. Tell me it didn't effect your leg strength. I always combine both lifting and running. It's a compromise in both.